ListAdapter by RecyclerView with implementation Filterable

FilterableListAdapter.kt

abstract class FilterableListAdapter<Item>(
        callback: DiffUtil.ItemCallback<Item>
): ListAdapter<Item, RecyclerView.ViewHolder>(callback), Filterable {

    protected val rawItems = mutableListOf<Item>()
    protected var itemsNotFound: Boolean = false

    override fun getFilter(): Filter {
        return object: Filter(){
            override fun performFiltering(constraint: CharSequence): FilterResults {
                val filerResults = FilterResults()

                val items = if (constraint.isEmpty()) {
                    rawItems
                } else {
                    rawItems.filter {
                        isFilter(it, constraint)
                    }
                }

                filerResults.values = items
                filerResults.count = items.size

                return filerResults
            }

            override fun publishResults(constraint: CharSequence, results: FilterResults) {
                itemsNotFound = results.count == 0
                publishResult(results.values as List<Item>)
            }
        }
    }

    private fun publishResult(items: List<Item>){
        super.submitList(items)
    }

    private fun fillRawItems(list: List<Item>?){
        rawItems.clear()
        list?.let {
            rawItems.addAll(list)
        }
    }

    override fun submitList(list: List<Item>?) {
        fillRawItems(list)
        super.submitList(list)
    }

    override fun submitList(list: MutableList<Item>?, commitCallback: Runnable?) {
        fillRawItems(list)
        super.submitList(list, commitCallback)
    }

    abstract fun isFilter(item: Item, constraint: CharSequence): Boolean
}